Predetermined torque release wrench



July 14, 1964 w. E. VAN HoosE PREDETEEMINED ToEQuE RELEASE WRENCHyFiled. Aug. 29, 1961 United States Patent() 3,140,623 PREDETERMINEDTORQUE RELEASE WRENCH William E. Van Hoose, Bell, Calif., assignor, bymesne assignments, to Pendleton Tool Industries, Inc., Los Angeles,Calif., a corporation of Delaware Filed Aug. 29, A1961, Ser. No. 134,772Claims. (Cl. 81-52.4)

This invention relates generally to torque-applying tools and,particularly, to an improved predetermined torque release wrench.

One of the major difficulties in the design and manufacture of apredetermined torque release wrench is attaining accuracy and precisionin the release of the wrench under torque load while retainingsimplicity and economy of manufacture and assembly. VIn other words, thethree basic requirements of a torque wrench are (l) accuracy, meaningthat the wrench must release exactly at a specified applied torque loador exactly at each of the several applied torque loads for which thewrench may be preset to release, (2) precision, meaning that the appliedtorque load at which the wrench releases at any given torque releasesetting must repeat, i.e., remain constant during repeated release ofthe wrench at the given setting, and (3) simplicity and economy ofmanufacture, meaning that the wrench must be capable of being sold at areasonable cost.

A general object of this invention is to provide a predetermined torquerelease wrench which possesses both accuracy and precision of operationand yet is relatively simple in construction and economical tomanufacture.

Other objects, advantages,.and features of the invention will becomeevident as the description proceeds.

A presently preferred illustrative embodiment of the invention will nowbe described Vby reference to the attached drawing, wherein:

FIG. 1 is a longitudinal section through a predetermined torque releasewrench embodying Vthe improvements of this invention, showing the wrenchparts in their normal positions;

FIG. 2 is a view of the forward end of the wrench in FIG. l showing thewrench parts in the positions they occupy after release of the wrench;

FIG. 3 is a section taken along line 3--3 in FIG. 1; and

FIG. 4 is a section taken along line 4-4 in FIG. 1.

The predetermined torque release wrench illustrated in this drawing isequipped with a tubular handle 12. Handle 12 is flattened at its forwardend portion 12a in the usual way. Pivotally mounted on the forward endof the handle, for turning on a pivot axis 14 transverse to thelongitudinal axis 16 of the handle, is a torque transmission member 18through which a torque load is transmitted from the handle 12 to aworkpiece (not shown).

Torque transmission member 18 is journaled in aligned bearing holes inthe forward, ilat walls 20 of the handle and includes a square stud 22located exteriorly of the handle. This stud is shaped to receive variouswrench sockets or yother work-,engaging elements (not shown) in thewell-known way. Y

Extending longitudinally through the forward part of the handle 12 is atang or arm 24. Tang 24 has a square hole 26 into which the square bodyof the torque transmission member 18 is vpress fitted. Arm 24 is,therefore, rigid on the member 18 and'pivots with the latter. During theapplication of a torque Sload to a workpiece, the handle 12 is rotatedin aclockwise direction on the axis 14, as the wrench is viewed in thedrawing. The handle 12 and member 18 tend to rotate with respect to oneanother on the axis `14 as the torque load is applied, member 18 and arm24 tending *to rotate in the counterclockwise direction in the handle.

y 3,140,623 Patented July 14, 1964 ICC At the rear of arm 24 is aplunger 28 with which this invention primarily is concerned. Plunger 28is preferably in the form of a sleeve 30 for convenience of manufacture.Behind the plunger is a spring 32 which seats at its forward end againstthe rear end of the plunger sleeve 30. The rear end of spring 32 seatsagainst the forward end of a cylindrical part 34 which is slidable inthe wrench handle 12.but is keyed against rotation in the handle bymeans of aradial pin 36 in the part engaging ing in a longitudinal slot38 Vin the handle.

Threaded on the outside of the handle 12, at its rear end, is a sleeve40. A threaded insert 42 is fixed in the rear end of this sleeve. Insert42 has a central bore 44 through which extends a lock screw 46. Lockscrew 46 is threaded in the rear end of part 34 and is formed with arear enlarged head 48. Insert Ibore 44 is counterbored at its rear end,as shown, to receive the lock screw head. The lock screw is turnable bylgrasping a rib 50 thereon.

It is evident that when lock screw 46 is tightened, cylindrical part 34and insert 42 are clamped tightly together and sleeve 40 is therebylocked against rotation. When lock screw 46 is loosened, sleeve 40 maybe rotated with respect to the part 34 and on the handle 12. Rotation ofsleeve 40 in one direction advances the part 34 against the spring 32 toincrease the spring pressure on the plunger 28. Rotation of the sleevein the opposite direction retracts the part 34 rearwardly in the handleto relieve the spring pressure on the 4plunger 28.,

The forward end of the central opening-52'through the plunger 28 forms arecess in which is positioned a casehardened cam roller 54. Roller 54 isarranged with its central axis approximately normal to the plunger axisand approximately parallel to the pivot axis 14. Extending axiallythrough the camv roller 54 is an axle pin 56 on which the roller isrotatable. The ends of pin 56 are supported in the plunger 28. Roller 54projects slightly-beyond the forward end of the plunger, as shown. Theforward end of the plunger is beveled slightly at 58 to clear arm 24 asthe latter swings in the handle.

Fixed in the rear end of the rarm 24, as by being press fitted in acutaway bore 60 extending through the arm parallel to the pivot axis 14,is a casehardened pin 62. Pin 62 provides a cam element engageable withthecam roller 54. Threaded in the rear end of the arm 24, and extendingabout normal to the pivot axis 13, is a calibration screw 64.Calibration screw 64 is .accessible through a hole 66 in the handle 12,which hole may be closed by a screw 68.

In the normal position of the -wrench parts illustrated in FIG. 1, camroller 54 is disposed in the path along which the rear end of arm 24moves during relative counterclockwise (as the wrench is viewed in thedrawing) rotation of the arm in the handle. When a torque load is firstapplied to a workpiece, by clockwise rotation of handle 12, cam pin 62on the arm 24 engages the 'cam roller and the latter blocks relativerotation of the handle 12 and torque transmission member 18 on the pivotaxis 14. Member 18 is, therefore, forced to rotate in the clockwisedirection with the handle so that the torque which is applied to thewrench handle is `transmitted through the member 18 to the workpiece.

As the torque load is applied, cam pin` 62 presses againstthe curvedsurface of the cam roller 54. A caniming action is thereby created whichproduces a rearward force component on plunger 28 tending to move thelatter rearwardly in the handle 12 against the action of the spring 32.As the torque load increases, the rearward camming force on the plungerincreases. Eventually the latter force overcomes the spring pressure onthe plunger, whereupon the latter is suddenly forced rearwardly and thearm 24 is released to swing in the counterclockwise direction in thehandle. In other words,

the wrench releases What actually happens when the wrench releases, ofcourse, is that the arm 24 and torque transmission member 18 remainstationary while the handle 12 rotates slightly in the clockwisedirection.

This sudden release of the wrench handle affords a rst indication thatthe predetermined torque load has been reached. A second indication thatthe predetermined torque load has been reached is afforded by the clickwhich occurs when, after release of the handle, the latter rotates intoimpact with the rear end of the arm 24 (FIG. 2).

In the released position of the wrench parts, shown in FIG. 2, the campin 62 has not quite reached a deadcenter position on the cam roller 54.As a result, when the applied torque is removed from the wrench handle,a reverse camming action is developed on the pin 62, by virtue of thespring pressure of the cam roller 54 thereagainst, which returns thewrench parts to their normal position of FIG. 1.

Proceeding now to the improvement features of the present invention, itwill be observed that the camming action which occurs between the camroller 54 and carn pin 62 during the application of a torque load to aworkpiece creates on the plunger 28 not only the rearward camming forcediscussed above but also a lateral camming force, or, more strictlyspeaking, a lateral force component. This lateral force component forcesthe plunger upwardly and toward the upper inner surface of the wrenchhandle 12, as the wrench is viewed in the drawing. If the plunger wereforced directly against the inner surface of the handle, the resultingfriction between the wrench handle and the plunger, which would varywith the applied torque as well as with other factors, would introduceerror into the wrench operation and cause a loss of both accuracy andprecision.

The present invention proposes to reduce to a minimum the frictionalforces acting on the plunger 28, and thereby maximize both the accuracyand precision of the wrench, as follows: Formed in the upper side of theplunger sleeve 30, adjacent the forward end of the sleeve, are twocircumferentially spaced bores or holes 70. These holes open into thecentral opening or recess 52 in the plunger opposite the cam roller 54.Bores 70 are proportioned to rotatably receive bearing balls 72 of sucha diameter that the balls will seat against the surface of the camroller and against the inner surface of the wrench handle 12. Balls 72thus project slightly beyond the outer surface of the plunger 28 andprovide a low friction rolling contact between the plunger and wrenchhandle.

The present ball bearing arrangement in which bearing balls 72 seatdirectly against the cam roller 54 has several advantages. In the firstplace, balls of greater diameter may be used than if the balls weresimply seated in depressions in the outer surface of the plunger, forexample. Bearing balls of greater diameter are desirable since they areless prone to crushing or other deformation under the loads imposed onthe balls in operation of the wrench. As a result, greater torque loadsmay be applied with the present wrench.

Another advantage of the present bearing ball and cam roller arrangementis that maximum rolling contact between the plunger 28 and wrench handle12 is achieved. Thus, the bearing balls 72 not only have rolling contactwith the wrench handle 12, but also with the cam roller 54. It will beobserved that since movement of cam pin 62 past cam roller 54 duringrelease of the wrench tends to turn the roller in the clockwisedirection in FIGS. 1 and 2 and the friction between the handle andbearing balls 72 tends to rotate the balls in the counterclockwisedirection during rearward movement of the plunger 2S in the handle, thebearing balls and cam roller move in the same direction at their pointsof contact. There is, therefore, primarily rolling contact between thecam pin 62 and cam roller 54, between the cam roller and bearing balls72 and between the bearing balls and the inner surface of the handle.Moreover, it will be observed that during the application of a torqueload, the lateral thrust on the plunger is transmitted from the cam pin62 to the cam roller 54, from the cam roller to the bearing balls 72,and from the bearing balls to the wrench handle 12. Thus, there islittle, if any, lateral load transmitted through the plunger sleeve 30so that no part of the sleeve is urged with any great force against theinner surface of the wrench handle. As a result, frictional resistancebetween the plunger 28 and wrench handle is appreciably minimized,whereby the accuracy and precision of the wrench are maximized.

The present wrench construction is obviously relatively simple andeconomical to manufacture and assemble.

The torque release value of the wrench is adjusted in the usual way byrotating the sleeve 40 to vary the pressure of the spring 32 against theplunger 28. Suitable indicia (not shown) are provided on the wrenchhandle 12 and sleeve 40 to indicate various predetermined settings ofthe wrench. Screw 64 is used to calibrate the wrench. Thus, adjustmentof the calibration screw 64 shifts the point of contact of the cam pin62 with the cam roller 54 around the axis of the roller. This has theeffect of changing the rearward force component on the plunger 28 forany given pressure of the cam pin 62 against the roller surface and,therefore, the torque release value of the Wrench.

While the illustrated Wrench utilizes ball bearings between the camroller and wrench handle, a. needle bearing might be used by making theinner surface of the handle engaged by the bearing flat rather thancylindrical and providing the plunger with an opposing at rather thancylindrically curved surface. In this case, of course, the plunger wouldbe provided with a transverse slot to receive the needle bearing ratherthan circumferentially spaced holes as in the illustrated wrench.

Clearly, then, the invention is capable of attaining the objects andadvantages preliminarily set forth.

What is claimed is:

l. A predetermined torque release wrench, comprising:

a tubular handle,

a Work-engaging member rotatably mounted on said handle for turning on atransverse axis of the handle,

an arm rigidly secured at one end to said member and extendinglongitudinally through said handle,

a plunger longitudinally movable in said handle opposite the other endof said arm,

a rst roller on the end of said plunger adjacent said other end of saidarm,

a spring acting between said handle and plunger for urging the lattertoward said arm to a position wherein the curved surface of said rollerengages said other end of said arm to releasably restrain the latter andsaid member against turning in one direction with respect to saidhandle, whereby an applied torque which tends to turn said arm andmember in said one direction relative to said handle creates alongitudinal camming force on said plunger tending to retract the latteragainst the action of said spring and thereby release said arm andmember for rotation in said one direction relative to said handle, and alateral thrust on said roller directed toward one side of said handle,

said plunger including a longitudinally extending wall between saidroller and said one side of said handle, and said wall having an openingopposite said roller, and

a second roller in said opening seating against said rst roller and theinner surface of said handle, whereby the lateral thrust of said armagainst said irst roller is transmitted directly through said rollers tosaid handle and said rollers cooperate to support said plunger for freelongitudinal movement in said handle.

2. A predetermined torque release wrench, comprising:

a tubular handle,

a work-engaging member rotatably mounted on said handle for turning on atransverse axis of the handle,

an arm rigidly secured at one end to said member and extendinglongitudinally through said handle,

a plunger longitudinally movable in said handle opposite the other endof said arm,

a rst roller on the end of said plunger adjacent said other end of saidarm,

a spring acting between said handle and plunger for urging the lattertoward said arm to a position wherein the curved surface of said rollerengages said other end of said arm to releasably restrain the latter andsaid member against turning in one direction with respect to saidhandle, whereby an applied torque which tends to turn said arm andmember in said one direction relative to Said handle creates alongitudinal camming force on said plunger tending to retract the latteragainst the action of said spring and thereby release said arm andmember for rotation in said one direction relative to said handle, and alateral thrust on said roller directed toward one side of said handle,

said plunger including a longitudinally extending wall between saidroller and said one side of said handle, and said wall having a pair ofopenings spaced transversely of said plunger and located opposite saidroller, and

second rollers in said openings, respectively, seating against saidfirst roller and the inner surface of said handle, whereby the lateralthrust of said arm against said irst roller is transmitted directlythrough said rollers to said handle and said rollers cooperate tosupport said plunger for free longitudinal movement in said handle.

3. A predetermined torque release wrench, comprising:

a tubular handle,

a work-engaging member rotatably mounted on said handle for turning on atransverse axis of the handle,

an arm rigidly secured at one end to said member and extendinglongitudinally through said handle,

a plunger longitudinally movable in said handle opposite the other endof said arm,

a generally cylindrical roller mounted on the end of said plungeradjacent said other end of said arm with the axis of said rollerextending approximately parallel to said turning axis of saidWork-engaging member,

a spring acting between said handle and plunger for urging the lattertoward said arm to a position wherein the curved surface of said rollerengages the other end of said arm to releasably restrain the latter andsaid member against turning in one direction with respect to saidhandle, whereby an applied torque which tends to turn said arm andmember in said one direction relative to said handle creates alongitudinal camming force on said plunger tending to retract the latteragainst the action of said spring and thereby release said arm andmember for rotation in said one direction relative to said handle, and alateral thrust on said roller directed toward one side of said handle,

said plunger including a longitudinally extending wall between saidroller and said one side of said handle, said wall having a pair ofopenings spaced in the axial direction of and located opposite saidroller, and

bearing balls in said openings, respectively, seating against saidroller and the inner surface of said handle, whereby the lateral thrustof said arm against said roller is transmitted directly through saidroller and bearing balls to said handle and said roller and ballscooperate to support said plunger for free longitudinal movement in saidhandle.

4. A predetermined torque release wrench, comprising:

a tubular handle,

a work-engaging member rotatably mounted on said handle for turning on atransverse axis of the handle,

an arm rigidly secured at one end to said member and extendinglongitudinally through said handle,

a plunger longitudinally movable in said handle opposite the other endof said arm,

a roller on the end of said plunger adjacent said other end of said arm,

a hardened pin carried on said other end of said arm and extendingapproximately parallel to said turning axis, and

a spring acting between said handle and plunger for urging the lattertoward said arm to a position wherein said roller engages said pin toreleasably restrain said arm and member against turning in one directionwith respect to said handle, whereby an applied torque which tends toturn said arm and member in said one direction relative to said handlecreates a longitudinal camming force on said plunger tending to retractthe latter against the action of said spring and thereby release saidarm and member for rotation in said one direction relative to saidhandle.

5. The subject matter of claim 4, wherein:

said pin is frictionally held in a generally semi-circular groove insaid other end of said arm and protrudes through the open side of saidgroove into contact with said roller.

References Cited in the tile of this patent UNITED STATES PATENTS2,704,472 Booth Mar. 22, 1955 2,887,921 Livermont May 26, 1959 2,918,834Cranford Dec. 29, 1959 2.972,271 Gill Feb. 21, 1961

1. A PREDETERMINED TORQUE RELEASE WRENCH, COMPRISING: A TUBULAR HANDLE,A WORK-ENGAGING MEMBER ROTATABLY MOUNTED ON SAID HANDLE FOR TURNING ON ATRANSVERSE AXIS OF THE HANDLE, AN ARM RIGIDLY SECURED AT ONE END TO SAIDMEMBER AND EXTENDING LONGITUDINALLY THROUGH SAID HANDLE, A PLUNGERLONGITUDINALLY MOVABLE IN SAID HANDLE OPPOSITE THE OTHER END OF SAIDARM, A FIRST ROLLER ON THE END OF SAID PLUNGER ADJACENT SAID OTHER ENDOF SAID ARM, A SPRING ACTING BETWEEN SAID HANDLE AND PLUNGER FOR URGINGTHE LATTER TOWARD SAID ARM TO A POSITION WHEREIN THE CURVED SURFACE OFSAID ROLLER ENGAGES SAID OTHER END OF SAID ARM TO RELEASABLY RESTRAINTHE LATTER AND SAID MEMBER AGAINST TURNING IN ONE DIRECTION WITH RESPECTTO SAID HANDLE, WHEREBY AN APPLIED TORQUE WHICH TENDS TO TURN SAID ARMAND MEMBER IN SAID ONE DIRECTION RELATIVE TO SAID HANDLE CREATES ALONGITUDINAL CAMMING FORCE ON SAID PLUNGER TENDING TO RETRACT THE LATTERAGAINST THE ACTION OF SAID SPRING AND THEREBY RELEASE SAID ARM ANDMEMBER FOR ROTATION IN SAID ONE DIRECTION RELATIVE TO SAID HANDLE, AND ALATERAL THRUST ON SAID ROLLER DIRECTED TOWARD ONE SIDE OF SAID HANDLE,SAID PLUNGER INCLUDING A LONGITUDINALLY EXTENDING WALL BETWEEN SAIDROLLER AND SAID ONE SIDE OF SAID HANDLE, AND SAID WALL HAVING AN OPENINGOPPOSITE SAID ROLLER, AND A SECOND ROLLER IN SAID OPENING SEATINGAGAINST SAID FIRST ROLLER AND THE INNER SURFACE OF SAID HANDLE, WHEREBYTHE LATERAL THRUST OF SAID ARM AGAINST SAID FIRST ROLLER IS TRANSMITTEDDIRECTLY THROUGH SAID ROLLERS TO SAID HANDLE AND SAID ROLLERS COOPERATETO SUPPORT SAID PLUNGER FOR FREE LONGITUDINAL MOVEMENT IN SAID HANDLE.